1956 Ariel square 4 runs great, starts first kick. Everything on the bike works well. It does need front fork seals they are leaking a bit.

It comes with a clear Texas title. Please ask questions

That’s it, the whole listing. Luckily, the photographs are bright and clear and show a bike in very nice condition. I’d love to know a bit about this bike’s history, updates and maintenance that have been done. I guess the seller figures prospective buyers already know all about these. In case you don’t I’ll fill you in a bit.

Produced between 1931 and 1959, Ariel’s Square Four began as a 500cc machine and ultimately grew to the 997cc machine you see here. Weighing in at a relatively light 425 pounds and producing 45bhp it can easily keep up with modern traffic, although limited cornering clearance and period brakes mean you should plan your maneuvers well in advance. While it isn’t necessarily much faster than some of the bigger twins and singles of the period, the four was obviously smoother with a wider spread of power.

Keep in mind that four cylinder motors were considered very exotic until Honda and Kawasaki flooded the market with them in the early 1970’s. Twins and singles ruled the motorcycle world for the most part, and the square four was a way to introduce the smoothness and power of a four into existing frames originally designed to hold singles.

Like the square four two-stroke race replicas of the 1980’s, the Ariel is quite simply two parallel twins with their cranks geared together sharing a single head. Early bikes tended to overheat the rear cylinders, as you might expect, since they were blocked from receiving any cooling airflow. Later revisions to the bike addressed this, although it was always a weakness of the design.

The later examples were known as “four pipe” bikes for obvious reasons: note the four separate exhaust pipes coming out of the head. In addition, the Mark II redesign featured extensive use of aluminum for the block and head, saving 30lbs over the earlier models.

The buy it now price is set at $21,000 which pretty big money. Ebay indicates several offers have been made, but I’d expect they were pretty far off the asking price, which seems a bit steep, even for a bike this nice.